1. Field of the Invention
The present invention relates to an image processing device and an image processing method, an in particular, relates to an image processing device and an image processing method which process input image data by an error diffusion method.
2. Description of Related Art
To reproduce an image, an electrophotographic printer processes image data by an error diffusion method. In this case, when black isolated points and white isolated points generate, reproducibility of dots relating to the isolated points becomes unstable. As a result, there are many cases in which tone reproducibility deteriorates. In particular, there are many cases in which tone in a highlight part and a dark part deteriorates, and compared with a case in which an image processing is carried out by an ordered dither method, there are many cases in which density reproducibility of halftone deteriorates. Meanwhile, the image processing by the ordered dither method has a drawback that moire, which is difficult to generate in the image processing by the error diffusion method, is prone to generate in a reproduced image.
A conventional technology relating to an image processing by an improved error diffusion method reduces noise in a highlight part and a shadow part (a dark part). According to this technology, when calculating a correction value to be added to input image data before a quantization processing, a threshold value and an error amount in the quantization processing are fluctuated.
According to the conventional technology, to calculate a quantization error and to calculate a correction error to be added to the input image data, a complicated processing is required to be carried out. As a result, a large burden is imposed on hardware for the processing.